Demands for improvement in system capacity are growing due to an increase in the amount of data used by users. A non-orthogonal transmission scheme is considered to be a solution to such demands. In particular, faster-than-Nyquist (FTN) signaling is favored as a non-orthogonal transmission method for increasing a data rate while simultaneously improving spectrum efficiency.
Here, FTN signaling is a transmission scheme in which symbols are transmitted at a rate higher than the Nyquist rate at which orthogonality between symbols is satisfied. That is, FTN signaling is a transmission scheme of transmitting time-domain sampling pulses at an artificially faster symbol rate than Nyquist signaling in order to break orthogonality between symbols.